Such a binding assures the safety of a skier by responding, through its lateral release, to excessive torsional forces at the level of the leg of the skier. The conventional types of safety bindings, of the lateral release type, have a certain number of disadvantages, particularly when a torsional fall is combined with a frontward fall. In effect, during a frontward shift of the weight of the skier, the bottom of the sole of the boot which is at the level of the front of the foot is applied against the ski with a substantial force directed thereto, i.e., downwardly, which serves to create, between the bottom of the sole and the support surface thereof, a substantial frictional force which opposes the lateral displacement of the boot.
A solution has long been sought to the problem of these safety bindings of the lateral release type, to provide a safety binding which maintains the boot without moving during normal skiing, i.e., a stable maintenance position of the boot, substantially in the longitudinal, vertical median plane of the binding, and which is laterally releasable in a sure fashion by reducing to the maximum the frictions between the sole of the boot and the upper surface of the ski.
It has thus been proposed to glue to the surface of the ski a plate made of an anti-stick material, such as described in French Patent No. 2 092 844, but the cleats or treads which may be provided under the sole of the boot considerably increase the friction, and dirt may render it beyond control.
To further diminish friction, it has been proposed to insert between the sole of the boot and the upper surface of the ski a movable support plate adapted to be laterally displaced with the boot. The sliding between the movable plate and the ski is in this case not disturbed by dirt or the cleats of the boot.
A first solution, described in WO85/03451, has involved utilizing a plate affixed to the binding. However, in this first case, if ice forms between the plate and the ski there is a blockage of the binding or at least a very substantial disturbance of its operation.
A second solution, described in Swiss Patent No. 490,871, has consisted in providing a rotatable plate, positioned on the upper surface of the ski, and returned to the central position by a recentering spring. The disadvantage is that during release of the binding the boot makes the plate pivot against the energy of its recentering spring. This energy is added to the energy of the binding and increases the force which the leg must overcome to obtain the release of the binding.